CHEMISTRY OF RIBOSE AND DEOXYRIBOSE 33 



Petrow and his colleagues'" measured the pKa at 25 ± 1° of 5,6-di- 

 methylbenzimidazole-l-j8-D-ribopyranoside and found a value in water of 

 4.70 at a dilution of 490 liters per mole. Benzimidazole glycosides are 

 less basic than the corresponding free benzimidazoles and in general the 

 basicity falls in the series 



l-/3-D-ribo- > 1-a-D-arabo- > 1-a-L-arabo- > l-/3-D-xylo-pyranose. 



Various methods have been used in connection with syntheses of ribo- 

 flavin-type compounds to prepare A^-ribityl derivatives.'**'*^ A^-3,4- 

 Dimethylphenyl-D-ribosylamine affords directly on hydrogenation 3,4- 

 dimethylphenyl-D-ribamine.'^^ Ribitylbenzimidazole derivatives have been 

 prepared as possible carcinolytic compounds: l-(l'-D-ribityl)-5,6-dimethyI- 

 benzimidazole was ineffective in producing regression of established lym- 

 phosarcoma implants in mice.'^' Because of the great interest in the nat- 

 urally occurring nucleosides, studies of the synthesis of D-ribosides of 

 purine and pyrimidines have been numerous [cf. Baddiley, Chapter 4.]. 



d. Phosphates 



Many biochemical reactions proceed by the agency of phosphorylated 

 derivatives of D-ribose (for reviews see Avison and Hawkins, '^^ and Foster 

 et al."^). [Cf. Glock, Chapter 22, and Schlenk, Chapter 24.] The present 

 account will be limited mainly to a description of the chemistry of the 

 monoorthophosphoric esters of ribose. Brief reference will be made to other 

 pentose phosphates, both for comparative purposes and because some were 

 suggested as components of nucleic acid, prior to the recognition of the 

 sugar moiety as D-ribose. For comparison of the properties and reactions of 

 pentose phosphates with those of hexose phosphates, disaccharide phos- 

 phates, etc., reference should be made to the excellent review of sugar 

 phosphates by Leloir.^ 



Several methods are available for differentiating between the various 

 phosphate esters of ribose. Like other aldose- 1 -phosphates, ribose- 1 -phos- 

 phate is very sensitive to acid treatment'^^ and in this respect resembles the 

 0-glycosides. Furthermore, like the glycosides, the /8-anomers of aldose-1- 



'" M. T. Davies, P. Mamalis, V. Petrow, and B. Sturgeon, J. Phann. and Pharmacol . 



3, 420 (1951). 

 '«« M. Tishler and J. W. Wellman, U. S. Pat. 2,261,608 (Nov. 4, 1941). 

 •»»R. Pasternack and E. V. Brown, U. S. Pat. 2,237,263 (April 1, 1941). 

 "» R. Kuhn and L. Birkofer, Ber. 71, 621 (1938). 

 '7' F. W. Holly, Elizabeth W. Peel, J. J. Cahill, and K. Folkers, J. Am. Chem. Soc. 



73, 332 (1951). 

 '" A. W. D. Avison and J. D. Hawkins, Quart. Revs. (London) 5, 171 (1951). 

 '" A. B. Foster, W. G. Overend, and M. Stacey, Die Starke 5, 285 (1953). 

 '" H. M. Kalckar, J. Biol. Chem. 167, 477 (1947). 



